A significant discovery
In the Soa Basin of central Flores, a layer of sandstone records the history of the deep past. In 2014, researchers excavating at a site called Mata Menge pulled a fossilized mandible fragment and six teeth from this layer. These were fossils; they belonged to a tiny hominin that lived around 700,000 years ago. The age was determined by dating the layers of volcanic ash that sandwiched the fossil-bearing sandstone. Methods like argon-argon dating and fission track dating on the volcanic deposits provided a secure timeframe for when these individuals lived.
The fossils, which represent at least three separate individuals including two children, are the oldest hominin remains ever found on the island of Flores. Their discovery dramatically pushed back the known timeline of hominin occupation. Their anatomy suggests they were direct ancestors of Homo floresiensis, the famous "hobbit" discovered in 2003 at Liang Bua cave, 74 kilometers away. The Mata Menge jaw is about 20% smaller than the already small mandible of the much later Liang Bua hobbit, indicating that extreme shrinkage, a process called insular dwarfism—was well underway half a million years earlier than previously known. A recently found 700,000-year-old humerus (upper arm bone) from the site belonged to an adult estimated to be only about 100 cm tall.
Life on a Pleistocene island
The world of the Mata Menge hominins was a savannah-like open grassland with a nearby wetland. They were not alone. The excavations also unearthed a collection of other animal fossils, showing the local ecosystem. Among the finds were the remains of a pygmy Stegodon (an extinct relative of elephants), crocodiles, and giant rats called Hooijeromys. The dwarfing of large mammals like the Stegodon and the increase in size of smaller animals like rats are classic examples of the "island rule" in evolution.
These tiny hominins were also toolmakers. Over 500 simple stone artifacts have been found in the same layers as the fossils. The tools are described as simple flakes struck from a larger stone core, made from local materials like chert and volcanic rock. This technology is very similar to the tools found with the later Homo floresiensis at Liang Bua, showing a long-standing technological tradition on the island. The evidence suggests that a population of early hominins, likely Homo erectus, became stranded on Flores perhaps a million years ago and began a dramatic evolutionary process of shrinking in size to adapt to the island's limited resources.